Where she is pooping – the couch and the near the toilet, is very much territorial. Couches, beds and chairs hold our scent, and well, the bathroom…we won’t go there. But she is marking these places on purpose. There are two reasons why bunnies do this. One is to claim the area, the other reason could be that she is just sending the message that she is also part of the family. Their wild cousins do this for the same reasons.
So right, now, what you need to do is let her know you are the dominant species in the house, and do not allow her on the couch. (you may not have to do this permanently, just until she gets it which could be months ) The moment she jumps on, you say off, and make her jump off, or put her down if she won’t go down on her own. Don’t give her the opportunity to jump up there without you noticing either. Some people have used the noisy things "snappy trainer" but it would startle ME so much! And I was always afraid it would hurt them.
So anyway, I had to ban Rucy and Jack from the couch a long time ago because they would occasionally pee or poo on the couch. But now, yhey may come up to visit or briefly explore, but everything in their body language tells me they know that they couch is already claimed by humans only. They never mark the couch, not even one little sneaky mark.